ABB REX521 Feeder and Motor Protection Relay for Medium-Voltage Distribution Systems
ABB REX521 Feeder and Motor Protection Relay for Medium-Voltage Distribution Systems
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Brand:ABB PLC Item No.:ABB REX521 Product Origin:Sweden Product Dimensions:177 × 177 × 201 mm Product Weight:4.0 kg Payment:T/T, Western Union, Credit Card Goods_stock:15 Shipping Port:Xiamen, China Lead Time:1-3 Days Condition:Brand New And Original Warranty:1 Year Certificate:COO
The ABB REX521 Feeder and Motor Protection Relay is a multifunction numerical protection device designed for medium-voltage distribution networks, motor feeders, and industrial substations. Manufactured by ABB, the REX521 provides integrated protection, control, monitoring, and measurement functions in a single relay.
The relay is widely used to protect feeders, motors, transformers, and busbars in utility and industrial power systems. It continuously monitors electrical parameters and quickly responds to abnormal conditions such as overcurrent, earth faults, phase imbalance, and thermal overload.
Although it is considered a legacy protection relay, the REX521 remains widely deployed in substations due to its reliable performance and robust design.
Specifications may vary depending on configuration and hardware options.
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Applications
The ABB REX521 relay is designed for medium-voltage protection and control in utility and industrial electrical networks.
Typical applications include:
Medium-voltage feeder protection
Industrial motor protection systems
Transformer backup protection
Busbar protection systems
Substation automation
Industrial distribution networks
Renewable energy grid connections
Advantages
Comprehensive Protection Functions
Provides overcurrent, earth-fault, phase imbalance, and thermal overload protection for feeders and motors.
Integrated Monitoring and Measurement
Measures current, voltage, power, and frequency for system supervision.
Reliable Industrial Design
Engineered for demanding environments in substations and heavy industrial applications.
Flexible Communication Integration
Supports IEC 60870-5-103, Modbus, and SPA-bus protocols for SCADA integration.
Event and Disturbance Recording
Provides event logs and disturbance records to help engineers analyze system faults.
Compact Panel Installation
Designed for easy installation in switchgear panels.
Technical FAQs
1. What is the main function of the ABB REX521 relay?
It provides protection, monitoring, and control for feeders and motors in medium-voltage networks.
2. What protection functions are included?
Overcurrent protection, earth-fault protection, phase imbalance detection, and thermal overload protection.
3. Where is the REX521 typically used?
In medium-voltage substations, industrial plants, and motor feeder protection systems.
4. Does the relay support communication protocols?
Yes, it supports IEC 60870-5-103, Modbus, and SPA-bus communication.
5. What current transformer ratings are supported?
Typical CT inputs include 0.2 A, 1 A, and 5 A.
6. What auxiliary power supply does the relay require?
24–250 V DC or 100–240 V AC depending on configuration.
7. Can the relay record system disturbances?
Yes, it includes event logging and disturbance recording functions.
8. Is the REX521 still used today?
Yes, although it is considered a legacy relay, many installations still operate it reliably.
9. What equipment can the relay protect?
Feeders, motors, transformers, and busbars.
10. Why choose the ABB REX521 relay?
Because it combines protection, control, measurement, and monitoring in a reliable multifunction relay.
